1. Field of the Invention
This invention relates to a technique for attaching working implements such as a front loader, a backhoe and a mower unit to a frame type tractor having an engine mounted in a front region and a transmission case in a rear region of a main frame extending longitudinally of the tractor.
2. Description of the Related Art
As disclosed in Japanese Patent Laying-Open Publication No. 2000-273901 and U.S. Pat. No. 6,056,502, for example, a complex working vehicle called a TLB (tractor-loader-backhoe) is known that has a front loader attached to the front of a tractor, and a backhoe attached to the rear of the tractor. This TLB has a tractor body of monocoque construction (integral construction) with a clutch housing connected to the rear wall of an engine, and a transmission case connected to the clutch housing. The tractor body is reinforced by reinforcing frames extending longitudinally thereof. The front loader is attached to forward portions of the reinforcing frames, while the backhoe is attached to rear portions of the reinforcing frames. In this type of TLB, the tractor body and the reinforcing frames bear their shares of loads such as excavating forces occurring during a backhoe operation, and loading forces occurring during a loader operation.
Japanese Patent Laying-Open Publication H11-332346 discloses a frame type tractor having an engine is mounted in a front region and a transmission case in a rear region of a body frame formed of a pair of right and left plates connected together by cross members. A mower unit may be suspended from an intermediate portion of the body frame. However, the body frame of such a frame type tractor is not very rigid, and attaching a backhoe to the rear of the body frame has been considered impossible. This is because, where a backhoe is attached to the rear of the body frame, torsional loads are applied from the backhoe to the body frame during a backhoe operation, and such loads act on a connection between the body frame and the transmission case and on the transmission case in a serious way. Further, the body frame requires a rollover protection system to be attached to a rear portion thereof. A technique is desired that reinforces the body frame in an efficient way, i.e. without unduly entailing complications of the body frame structure, weight increase or cost increase.
The object of this invention is to provide an efficient frame reinforcement for a frame type tractor having an engine mounted in a front region and a transmission case in a rear region of a main frame extending longitudinally of the tractor, thereby allowing working implements such as a front loader, a backhoe and a mower unit to be attached to the tractor.
The above object is fulfilled, according to this invention, by a frame type tractor having a backhoe mounting frame attached to a rear end of a main frame, and rollover protection system mounts arranged in upper portions of the backhoe mounting frame for fixedly supporting a rollover protection system. In this construction since a backhoe unit and a rollover protection system are attached to the same mounting frame, strength against reactions from the backhoe unit and strength of the rollover protection system mounts may be considered at the same time. Thus, an efficient reinforcement may be provided. For example, the rollover protection system also may be considered a strength member against reactions from the backhoe unit.
In a preferred embodiment of this invention, the backhoe mounting frame has a frame structure defining an inner space therein and including a pair of right and left side walls, a top wall interconnecting upper ends of the side walls, and a bottom wall interconnecting lower ends of the side walls, and the right and left side walls have the rollover protection system mounts and backhoe attaching portions for engaging and connecting the backhoe unit. This construction greatly increases the strength of the rollover protection system and the strength against reactions from the backhoe unit acting sideways.
Further, the backhoe mounting frame may include a top link mount for attaching a top link of a three-point link mechanism, and lower link mounts for attaching lower links of the three-point link mechanism, at least part of the transmission case being fitted in the inner space of the backhoe mounting frame. Then, an efficient reinforcement may be provided to secure strength of the three-point link mechanism, besides securing the strength of the rollover protection system mounts. With the transmission case being fitted in the inner space of the backhoe mounting frame, forces acting on the transmission case are mitigated.
Further, the main frame may include a pair of right and left elongate members, the main frame being reinforced by a sub-frame including sub-elongate members arranged laterally outwardly of the elongate members and connected at opposite ends thereof to the elongate members, mower suspending mechanisms for suspending a mower unit being arranged each between one of the right and left elongate members and one of the right and left sub-elongate members. The sub-frame may effectively distribute a load received from the backhoe unit, and increase strength against torsional forces.
Where the elongate members of the main frame have the mower suspending mechanisms for suspending the mower unit, the sub-frame could be obstructive. However, a space for accommodating each mower suspending mechanism is formed between the right or left elongate member and the right or left sub-elongate member. It is thus possible to attach to the main frame the mower suspending mechanisms having a sufficient lifting height.
Rollover protection system mounts are provided for right and left props of the rollover protection system. These rollover protection system mounts are connected to each other. This further increases the strength of the rollover protection system against reactions from the backhoe unit acting sideways.
In a preferred embodiment of this invention, rear wheels are arranged laterally of the transmission case, the rear wheels, the backhoe mounting frame and the rollover protection system being arranged substantially in one vertical plane.
Despite the presence of the backhoe mounting frame, the distance between the transmission case and the rear end of the main frame is short. A weight balance does not deteriorate significantly even when the backhoe unit is attached.
In another embodiment of this invention, frame reinforcing units are provided for connecting upper portions of the backhoe mounting frame to portions of the main frame remote from the backhoe mounting frame. In this construction, the main frame, backhoe mounting frame, rollover protection system mounts and frame reinforcing units form a large truss structure in the rear of the main frame to secure strength of the rollover protection system against forces applied from rearward directions and to secure strength for withstanding a reaction from the backhoe unit attached to the rear of the main frame.
The object of this invention may be fulfilled also by a frame type tractor having a backhoe mounting frame attached to a rear end of a main frame, in which the main frame includes a pair of right and left elongate members, at least one cross member interconnecting the elongate members, and a first reinforcing cross unit and a second reinforcing cross unit interconnecting the elongate members forwardly and rearwardly of the transmission case. With this construction, excavating reactions occurring during an excavating operation performed by the attached backhoe unit are received by a frame structure formed of the right and left elongate members, the first reinforcing cross unit and the second reinforcing cross unit. Since no great load is applied to the transmission case, the transmission case may be formed of a light alloy such as an aluminum alloy, to contribute to lightening of the tractor body.
Each of the first reinforcing cross unit and the second reinforcing cross unit may have an integral construction. However, each cross unit, preferably, includes two substantially L-shaped halves respectively having vertical portions and horizontal portions, the two halves being connectable to and disconnectable from each other. Then, any assembly errors in the elongate members and transmission case may be absorbed reliably and efficiently by using assembly jigs and the like. The first reinforcing cross unit and second reinforcing cross unit may be formed of a pressed material or cut plate. However, the cross units, preferably, are formed of cast steel (or other cast material). This provides an advantage in production (manufacture) while securing sufficient rigidity.
The frame type tractors to which the above reinforcing technique is applied according to this invention may have a front loader attached to the front, the rollover protection system and backhoe unit to the rear, and the mower unit to an intermediate portion.
Other features and advantages of this invention will be apparent from the following description of the embodiment to be taken with reference to the drawings.